1. Field
An aspect of the invention relates to a magnet unit for a magnetron sputtering system.
2. Description of the Related Art
A magnetron sputtering system has generally been used to form various thin films on a substrate, such as a semiconductor substrate. The magnetron sputtering system performs sputtering using plasma while generating a magnetic field in the vicinity of the surface of a target, which is a sputtering material. A rotary magnet cathode is used to effectively utilize a target and form a uniform thin film by sputtering the target. The rotary magnet cathode is a device that rotates a plurality of permanent magnets on the rear surface of the target to rotate a magnetic field having a predetermined pattern in the vicinity of the front surface of the target. In order to generate the magnetic field having a predetermined pattern, a magnet unit formed by arranging a plurality of permanent magnets in a predetermined pattern is used.
The plurality of permanent magnets are arranged in a predetermined pattern such that the target is effectively sputtered. In the same arrangement of the magnets, the sputtering speed of the target or the deposition rate of the target on the substrate depends on the process conditions or the kind of target used during sputtering. Therefore, in this case, the arrangement of the magnets according to the process conditions or the kind of target can be changed. In order to change the arrangement of the magnets, some or all of the permanent magnets provided in the magnet unit can be removed, and the positions where the permanent magnets are attached changed. Hereinafter, the magnet unit to which the permanent magnet is detachably attached is referred to as a detachable magnet unit.
In many cases, a magnet unit according to the related art includes a base plate to which the permanent magnets are fixed. The base plate is formed of a magnetic material, and serves as a yoke through which magnetic flux generated from the permanent magnet passes.
Therefore, a detachable magnet unit has been proposed in which a groove is formed in a base plate, serving as a yoke, and the yoke having the permanent magnet attached thereto is fitted into the groove of the base plate and then screwed to the base plate such that it can be detached from the base plate (for example, see Patent Document 1).
Further, a detachable magnet unit has been proposed in which a pair of permanent magnets are fixed to a yoke member to form a detachable magnet part, and a plurality of detachable magnet parts are screwed to a base plate (for example, see Patent Document 2).